I want to install a simple motion sensor (Lutron Maestro MS-OPS2) on a single pole switch in my garage. When I installed it the light would not turn off. The instructions (PDF) that come with the motion sensor say this is a result of the ground not being connected (PDF). I double checked and the sensor was connected to the ground wire (bare copper wire) coming into the box. Does this mean that my ground wire is not connected to anything on the other end? How can I ground this switch so that I can get my motion sensor to work properly?

  • What is the make and model of the switch? Were you in the room when the light wouldn't turn off?
    – Tester101
    Commented Oct 21, 2013 at 15:59
  • You'll need to use a contact tester to check for voltage between the hot and ground wires. Be sure to take precautions to avoid being electrocuted.
    – BMitch
    Commented Oct 21, 2013 at 16:18
  • Switch is a Lutron Maestro MS-OPS2. No I was not in the room when it would not turn off. Here is the link to the user installation guide.
    – AJones
    Commented Oct 21, 2013 at 16:32
  • User installation guide lutron.com/TechnicalDocumentLibrary/0301654.pdf also here is the link for tech support that says if the light doesnt turn off then it means a disconnected ground (or it could be a disconnected nuetral but I already check that). lutron.com/TechnicalDocumentLibrary/3682373.pdf
    – AJones
    Commented Oct 21, 2013 at 16:34
  • What type of bulb is controlled by this sensor? Incandescent? CFL? LED? Neon? HID? Commented Aug 18, 2014 at 15:14

2 Answers 2


This type of switch requires a small amount of power to operate, and since there is not always a return path available for constant power. This switch uses the grounding conductor as a current carrying conductor, and dumps a small amount of power to the grounding conductor. It's not the best design; in my opinion, but if the standards and safety organizations approve it it must be safe.

Because of this awful design, a solid connection to earth is required for this switch to function. Which in your case, seems to be missing. It sounds like there is a grounding conductor included in the cable assembly at the switch box, so I'd start by tracing the cable back to where it originates. Follow the cable back to the nearest junction, whether that be another device or the service panel. Open up the junction point, and inspect the wiring. If everything looks good at that point, continue back down the line until you reach the service panel. You can use a tool like this Multi-Purpose Wire Tracer, to help trace the line through walls and ceilings.

Multi-Purpose Wire Tracer

If you reach the service panel, and all the connections along the way looked good. It means you likely have a break or some other damage to the grounding conductor inside the cable assembly. If this is the case, you'll have to locate the damaged section and replace it.

  • I guess I have some searching to do. I was hoping there would be an easier way but it is probably good I trace the ground wire and find the break. Who knows what else is not grounded. Thank you for your help.
    – AJones
    Commented Oct 22, 2013 at 18:43
  • Is it possible that the service panel isn't grounded through an exterior grounding rod? Could this cause the issue? When I had basement waterproofing done on my house, they pulled the 8' copper exterior grounding rod and didn't replace it until I noticed later and made them replace it as a condition of final payment.
    – rjbergen
    Commented Oct 17, 2014 at 16:53
  • @rjbergen Maybe. In the US the grounded "neutral" conductor of the service is typically grounded at the service equipment. So even without a grounding electrode, you'd still have a path for current to flow. More than likely, the grounding conductor for this circuit is not connected.
    – Tester101
    Commented Oct 17, 2014 at 17:04

I have faced a similar problem with the MS-OPS2. After talking to technical support and ruling out the "open ground" condition by running a jumper with to earth ground to the MS-OPS2's ground wire. Lutron technical support told me to get a different product offering (MS-OPS6M2N-DV-6) I said to myself "bullsh*t" it is just a switch. It works or it is bad. I replaced it with a Leviton and it works fine.


Not the answer you're looking for? Browse other questions tagged or ask your own question.